It has long been known the technique of coating by flame spraying thermoplastic powders applied by melting. Such technique is used for example for the production of anti-corrosive coatings on manufactured articles of different nature.
According to a known method, the thermoplastic powders are sprayed onto the manufactured article to be coated by means of a spray gun fed with compressed air and with a suitable liquefied petroleum gas. The gas flame produced by the spray gun transfers the melted particles of the powders onto the article to be coated.
The method of coating by flame spraying is of rapid and economic use and is suitable for coating different materials. The apparatuses currently used to obtain such coating, however, have certain drawbacks which limit their performance and thus make the use of the aforementioned method less effective.
In particular, it is often complained the fact that the spray gun is subject to overheating during its use. Such overheating causes an undesired adherence of the thermoplastic powders inside the gun, thus producing accumulations of powders about the outlet opening and inside the walls of the gun. This can as well adversely affect the physical characteristics of the powders to be sprayed.
Another problem complained in the field concerns the safety related to the use of the spray guns. In particular, with known spray guns, the ignition of the flame is performed by hand, by bringing an ignition device such as a lighter or a struck match at the exit of the gas from the spray gun. This obviously entails a high risk of accident.
Moreover, there exists the risk of accidental extinguishment of the flame during the use, which causes the supply of air and flammable gas in the environment. This entails a serious risk for users of the flame spray gun, as well as for the safety of those present in the surrounding environment.